Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $74.51   3.820%   $77.3563   $77.36   $77.35   $77.40  
  Purchase #2 $148.90   13.455%   $168.9345   $168.93   $168.95   $168.90  
  Purchase #3 $110.51   5.850%   $116.9748   $116.97   $116.95   $117.00  
  Purchase #4 $181.29   6.282%   $192.6786   $192.68   $192.70   $192.70  
  Purchase #5 $174.85   13.194%   $197.9197   $197.92   $197.90   $197.90  
  Purchase #6 $158.45   3.628%   $164.1986   $164.20   $164.20   $164.20  
  Purchase #7 $105.34   8.799%   $114.6089   $114.61   $114.60   $114.60  
  7 purchase totals = $953.85       $1,032.6714   $1,032.67   $1,032.65   $1,032.70